Routing devices within a network, often referred to as routers, maintain routing information that describe available routes through the network. Upon receiving an incoming packet from a client device, the router examines information within the packet and forwards the packet in accordance with the routing information. The router may continually receive and forward packets throughout the network, and some routers may have high availability features that provide client devices with a high level of access to routing services. In other words, routers having high availability features do not fail to provide routing services as often as other routers.
Generally, routers having high availability features provide a high level of access by maintaining redundant hardware components. For example, a router may include active line cards to receive and forward the packets, and redundant line cards to assume responsibility for the operations of any of the active line cards should one or more of the active line cards fail. The router may keep the redundant line cards warm, i.e., operational but not active, by replicating the configuration changes of the active line cards to the redundant line cards. Thus, in the event that one of the active line cards fails, the router may quickly transfer control to one of the redundant line cards, thereby allowing the router to offer continued routing services despite failure of one of the active line cards.
Routers that provide high-availability routing services are typically more expensive than standard routers because of the added cost incurred by including the redundant hardware components. As a result, some routers include a single redundant line card for multiple active line cards in an attempt to reduce the cost of the high level access features. If the number of failing active line cards exceeds the number of redundant line cards, the router may still fail to offer routing services.